The invention relates to the use of specific tripeptides for the treatment of postlesional diseases of ischemic, traumatic or toxic origin. The tripeptide derivatives satisfy the following formula (I): (see formula I as in paper form) wherein X represents OH, (C.sub.1-5) alkoxy, NH.sub.2, NH--C.sub.1-5-alkyl, N(C.sub.1-5 alkyl).sub.2; R.sub.1 is a residue derived from one of the amino acids Phe, Tyr, Trp, Pro, which each may be optionally substituted with one or more (C.sub.1-5) alkoxy groups, (C.sub.1-5) alkyl groups or halogen atoms, as well as Ala, Val, Leu or Ile; R.sub.2 is a residue derived from one of the amino acids Gly, Ala, Ile, Val, Ser, Thr, and Pro; Y.sub.1 and Y.sub.2 independently from each other represent H or (C.sub.1-5) alkyl; R.sub.3 and R.sub.4 independently from each other represent H, OH, (C.sub.1-5) alkyl or (C.sub.1-5) alkoxy, provided that R.sub.3 and R.sub.4 are not both OH or (C.sub.1-5) alkoxy; and R.sub.5 represents H, OH, (C.sub.1-5) alkyl or (C.sub.1-5) alkoxy; or a pharmaceutically acceptable salt thereof.